Recently, an internet is widely used and business activity of the internet is concerned. Especially, information transmission through the world is easy for the user by WWW. An activity of public information or propaganda is executed by low cost. Therefore, the user can participate in the business by using the network.
Normally, in a commercial transaction, credit to trade party is regarded as a base. For example, in trade between companies, a contract for cooperation relation is previously made as a commercial custom to limit the trade party. Furthermore, in a personal commercial transaction, a discreditable guest is discriminated by a confidence inquiry of a credit card and a creditable guest is secured by using a guest card. Accordingly, a method how to treat this credit is important in the business of a network society. This credit includes the credit for the buyer and the credit for the seller. The credit for the buyer is a credit for the buyer's payment ability. In same way of the buyer's confidence inquiry for credit card, the confidence inquiry is possible by checking the buyer's payment status in past.
On the other hand, the credit for the seller is a credit for a product or a service of the seller. The buyer actually decides by watching the product in a shop or by obtaining information through mass media. This method is not a problem in case the buyer's selection area is limited. However, in the network society, the commercial area is spread all over the world and the user can personally participate in the business. In short, any user can be the buyer and a number of the buyer greatly increases. Furthermore, in a virtual shop of the network, the user can not actually watch the product. Therefore, a new method to inquiry the seller's confidence is necessary.
As one solution method, a public company can present the credit information of all sellers. However, evaluation of the credit is often different by each public company and standarized evaluation is not always desired for the buyer. As another solution method, a plurality of the buyers can cooperatively exchange the credit information based on past trade result. However, the past trade result is secret between the companies. Therefore, a disclosure of the past trade result includes disadvantage aspect and this solution method is not realistic.